Method of producing gr-s latex containing carbon black



polymerization has been completed as by adding solution and potassium persulfate, styrene, modi- I St METHOD OF PRODUCING GR- S LATEX CONTAINING CARBON BLACK Rexford 1E. Draman, Akron, Ohio, assignor to The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ghio No Drawing. Application April 30, 1945, Serial No. 591,229

1 Claim. (Cl. 260-23.?) r a 2 This invention relates to producing a synthetic the black to the latex or milling it into the coagulatex by polymerizing in the presence of carbon lum. black. More particularly, it relates to such a EXAMPLE l process in which a hydrocarbon-soluble catalyst The process is preferably carried out in ro- 15 employed to counteract at least m part the 5 ducing separate suspensions of the blaci and retarding efiect of the carbon black on the polythe monomer monomers to be polymerized and merization reaction. Preferably, the hydrocarthen mixing. The formula, therefore may be bon'soluble catalyst is used with divided into two parts which refer respectively, a water-soluble catalyst. The invention includes to the black Suspension and the nnonomer tile new latex as well as the process of producing pension The fonawmg is illustrative:

In view of the difiiculty experienced in milling PART 1 carbon black and other pigments into synthetic Black suspensi n rubbers, considerable work has been done toward incorporating the black at some earlier stage of P t b the procedure. No one has heretofore success- Ingredients wti m fully polymerized one or more monomers in the ice presence of suspended carbon-black particles to Carbon black 111.2

produce a latex of a synthetic rubber in which fi-g the black particles are embedded in the suspended 2o Sulfonated mum-"- 5416 particles of the synthetic rubber. According to NHOH this invention carbon black is incorporated in a synthetic latex in this manner, and in a preferred PART B form of the invention the polymerization is car- Monomer suspension ried out in the presence of a hydrocarbon-soluble catalyst in conjunction with a water-soluble cata- Ingredients Pam by lyst. The effect of the catalysts is to ofiset or Weight counteract the retarding action of the carbonblack particles on the polymerization reaction. g a 889-0 pa 37.0

The hydrocarbon-soluble catalyst may be acrylo- Potassium persulfate. 3:0

nitrile, methyl vinyl ketone, benzoyl peroxide, ter- 5533333 58-8 tiary butyl hydroperoxide or the like. The water- Catalyst.-. 1133 soluble catalysts are of the type now employed in Butadiene" emulsion polymerizations, for example, hydrogen peroxide, potassium persulfate. other metallic The black mp10yed may be O p o S bla k. peroxides, other salts of persulfuric acid, perbo- The Soap 15 Preferably Sodlum Stearate, So rates, etc. oleate or the like. Instead of sulfonated tall oil Although the invention presently has more poany suitable dispersing agent be p oyed. tential value in the polymerization of butadiene h modlfier lauryl mercaptan y other and styrene to produce a latex Such as the well- 40 Stumble matenal' The catalyst is prefFrabl-y known GR-S latex, the invention is applicable nary butyl hydroperoxide Although in h also to the other polymerizations which yield rub- 2 3 3. g ig g g g g 1;; In bar-like latices for example in the cop 01ythe other rati hs e inp io e d in $311611; merization of butadiene and acrylonitrile, etc. like copolymers ma em ed In the latter reaction acrylonitrile, of course, is y p 037 P y mersmabade r not used as a catalyst although any other hydropolymersyabgve i g g iz m f replace the carbonsoluble catalyst may be In preparing the carbon-black suspensoid, the The amouPt of black whlch y be mcorpo materials were added in the following order: waratedaccording to this procedure will vary. Ortel. soap, dispersing agent, ammonium hydrox dinarily, not less than 5- parts nor more than 25 m and carbon black The black t into parts of black, by weight, per 100 parts of the inpension very easily, and fte fifteen minutes, t de p y W e added to t rebcticim agitation a very smooth emulsion was obtained. time prior to durlng e po y r a If In producing the emulsion for polymerization,

further black is to be added to the r b r, i Will the ingredients were added to the reaction vesordinarily be advantageous to do this after the sel in the following order: black suspensoid, soap fler and catalyst. and butadiene. The tertiary butyl hydroperoxide was dissolved in the lauryl mercaptan, and the two were added together.

An agitator was run in the reaction vessel during the addition of the black suspensoid. and the addition of the soap and catalyst. The soap and persulfate may be added together or separately. The agitator was turned oi! during the charging of the hydrocarbons but was started up again after the charging of the batch was completed. The reaction proceeded more slowly than a batch containing no black but otherwise progressed uneventfully. At the end of about 20 hours 43 per cent total solids (75 per cent conversion) had been reached. The reaction temperature was maintained at 125 F. for about 19 hours and was then raised to 135 F. to increase the slowing reaction rate. The latex showed no evidence of precoagulation or of carbon precipitation. It was quite viscous due to the high solids content.

After the polymerization was completed, the reaction mass was passed through the standard recovery equipment employed with GR-S reactions, and the recovery of unreacted monomers was rapid with less foaming than is usually encountered. Coagulation was accomplished in the usual manner with 2 per cent aluminum sulfate. The mother liquor was water white, indicating that the carbon black was embedded in the coagulum. The coagulum was filtered and dried without diflicuity.

Test samples were prepared according to the following formula:

Parts by weight GR-S 100 Channel black 50 Softener- 5 Zinc oxide 5 Sulfur 5 Mercaptobenzothiazole 2.5

Fifteen parts of the tabulated 50 parts of carbon black were charged to the reactor and-thus incorporated in the latex on polymerization, and the remaining 35 parts were added on the mill. The softener employed was a coal-tar product. The product was cured at 292 F. and tested as follows:

To determine the amount of catalyst to be used and whether a mixture of the hydrocarbon-soluble catalyst and water-soluble catalyst was better than either alone, two series of tests were run. The test bottles in each test were charged with identical components and treated identically for 16 hours at 122 1". The results of the two tests are not directly comparable but show the trend:

Pam Parts Per Cent mo. T. B. Conversion 3-: 3-2.... a mm Tm 010 012 as 0.0 0.333 100 3mm Tm 013 01134 as. a

by adding additional persulfate caused precoagulation of the latex. The hydrocarbon-soluble catalysts of this invention are, apparently, not adsorbed by the carbon black in the manner that water-soluble catalysts are; and the invention, therefore, lies in part in using such a hydrocarbon-soluble catalyst. The water-soluble catalyst may be omitted altogether. The preferred form of .the invention contemplates the use of a mixture of the two types of catalyst.

The water-soluble iron activators or kickers often used in ordinary polymerizations instead of the persulfate of the above formula cannot ordigarilg be employed in the presence of carbon The illustrations are not intended to limit the scope of this invention which is defined by the appended claim.

What I claim is: Y

The process of producing a latex of rubberlike copolymer of butadiene and styrene containing 5 to 25 parts of carbon black per parts of copolymer which comprises producing an aqueous suspension of the carbon black with a small amount of sodium-fatty-acid soap, sulfonated tall oil and ammonia; adding with agitation a small amount of sodium-fatty-acid soap and potassium-persulfate catalyst; then without agitation adding the styrene, the butadiene. and small amounts of lauryl-mercaptan modifier and tertiary-butyl-hydroperoxide catalyst, resuming agitation thereafter, and keeping the reaction mixture at a temperature of about F. until the reaction slows down and then raising the temperature to F.

REXFORD E. DRAMAN.

REFERENCES crran The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,911,672 Bock et al May 30, 1933 2,367,805 Semple Jan. 23, 1945 2,394,025 Te Grotenhuis Feb. 5, 1946 2,401,346 Fryling June 4, 1946 2,430,590 Stewart Nov. 11, 1947 OTHER REFERENCES Pages 577 to 582, The Rubber Age, Sept. 1944. (Copy in Div. 50.)

Pages 735 to 738, Industrial and Engineering 76 Chemistry, Aug. 1944. (Copy in Div. 50.)

Certificate of Correction Patent No. 2,476,819 July 19, 1949 REXFORD E. DRAMAN It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 46, for the word product read mix; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofiiice.

Signed and sealed this 31st day of January, A. D. 1950.

THOMAS F. MURPHY,

Am'atant Uommiuioner of Patents. 

